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><H1
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><A
NAME="CATALOG-PG-AM"
>45.3. <TT
CLASS="STRUCTNAME"
>pg_am</TT
></A
></H1
><P
>   The catalog <TT
CLASS="STRUCTNAME"
>pg_am</TT
> stores information about index
   access methods.  There is one row for each index access method supported by
   the system.  The contents of this catalog are discussed in detail in
   <A
HREF="indexam.html"
>Chapter 52</A
>.
  </P
><DIV
CLASS="TABLE"
><A
NAME="AEN84496"
></A
><P
><B
>Table 45-3. <TT
CLASS="STRUCTNAME"
>pg_am</TT
> Columns</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Type</TH
><TH
>References</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amname</TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
>&nbsp;</TD
><TD
>Name of the access method</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amstrategies</TT
></TD
><TD
><TT
CLASS="TYPE"
>int2</TT
></TD
><TD
>&nbsp;</TD
><TD
>Number of operator strategies for this access method,
       or zero if access method does not have a fixed set of operator
       strategies</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amsupport</TT
></TD
><TD
><TT
CLASS="TYPE"
>int2</TT
></TD
><TD
>&nbsp;</TD
><TD
>Number of support routines for this access method</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amcanorder</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support ordered scans sorted by the
       indexed column's value?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amcanorderbyop</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support ordered scans sorted by the result
       of an operator on the indexed column?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amcanbackward</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support backward scanning?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amcanunique</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support unique indexes?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amcanmulticol</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support multicolumn indexes?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amoptionalkey</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support a scan without any constraint
       for the first index column?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amsearchnulls</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does the access method support <TT
CLASS="LITERAL"
>IS NULL</TT
>/<TT
CLASS="LITERAL"
>NOT NULL</TT
> searches?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amstorage</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Can index storage data type differ from column data type?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amclusterable</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Can an index of this type be clustered on?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>ampredlocks</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
>&nbsp;</TD
><TD
>Does an index of this type manage fine-grained predicate locks?</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amkeytype</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-type.html"
><TT
CLASS="STRUCTNAME"
>pg_type</TT
></A
>.oid</TT
></TD
><TD
>Type of data stored in index, or zero if not a fixed type</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>aminsert</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Insert this tuple"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>ambeginscan</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Prepare for index scan"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amgettuple</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Next valid tuple"</SPAN
> function, or zero if none</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amgetbitmap</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Fetch all valid tuples"</SPAN
> function, or zero if none</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amrescan</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"(Re)start index scan"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amendscan</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Clean up after index scan"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>ammarkpos</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Mark current scan position"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amrestrpos</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Restore marked scan position"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>ambuild</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Build new index"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>ambuildempty</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
><SPAN
CLASS="QUOTE"
>"Build empty index"</SPAN
> function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>ambulkdelete</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
>Bulk-delete function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amvacuumcleanup</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
>Post-<TT
CLASS="COMMAND"
>VACUUM</TT
> cleanup function</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amcostestimate</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
>Function to estimate cost of an index scan</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amoptions</TT
></TD
><TD
><TT
CLASS="TYPE"
>regproc</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-proc.html"
><TT
CLASS="STRUCTNAME"
>pg_proc</TT
></A
>.oid</TT
></TD
><TD
>Function to parse and validate <TT
CLASS="STRUCTFIELD"
>reloptions</TT
> for an index</TD
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